The commonly used materials of central air conditioning air duct are rubber and plastic composite material, glass fiber reinforced plastics, galvanized iron sheet (insulation material in the middle, such as phenolic foam, polyurethane foam, glass fiber, etc., with a protective layer attached on the outside surface, such as aluminum foil, etc.).
The thermal conductivity of rubber plastic composite material is much lower than the thermal conductivity of galvanized iron duct, when the insulation material of galvanized iron duct long-term contact with air, there will be hygroscopic phenomenon, so that the thermal conductivity of galvanized iron duct greatly increased.In addition, the composite duct unique connection also ensures that the ventilation system has excellent air tightness, the leakage rate is only about 1/8 of the galvanized iron duct leakage rate.Therefore, the energy-saving effect of composite duct is much better than that of galvanized iron duct.
Field test shows that the heat loss of galvanized steel duct is about 15%, while the heat loss of rubber composite insulation material is less than 2%.
Galvanized iron sheet for inorganic materials, good fire performance, non-combustible A class, but the external often used rubber and plastic insulation materials.Due to the rubber insulation material fire performance only B1, so greatly reduced the galvanized iron duct fire grade.
The fire resistance of composite air duct varies according to different materials. For example, the fire resistance of modified phenolic foam aluminum foil air duct and glass fiber aluminum foil air duct has reached A level of noncombustible.
Therefore, from the perspective of fire performance, composite duct and galvanized iron duct can meet the fire requirements of household central air conditioning.
According to the provisions in the "code for construction and acceptance of ventilation and air conditioning engineering", when the diameter of air duct is less than 400 mm, the spacing is required to be no more than 4 m, while when the diameter of air duct is greater than or equal to 400 mm, the spacing is required to be no more than 3 m.For the household central air-conditioning, the diameter of the insulation duct is usually less than 400 mm, so its spacing as long as not more than 4 m can meet the requirements, and this condition is very easy to be met in the residential.That is to say, in general, rubber and plastic composite materials can fully meet the intensity requirements of household central air conditioning, do not need to be reinforced.
The outside of the galvanized iron duct needs to be wrapped with a layer of insulation layer on the site, and it is often needed to replace the insulation layer during maintenance, so in addition to the height of the duct itself, also need to reserve a certain amount of space for installation and maintenance.Composite duct itself has thermal insulation effect, and at the same time, the general use of invisible flange connection process, so you can close to the roof installation, no need to reserve installation space.Therefore, from the perspective of the impact on the height of the layer, the rubber and plastic composite duct is more suitable for household central air conditioning than galvanized iron duct.